One column is formatted like this: dd/mm/yyyy
The other is formatted like this: yyyymmdd
How do I create a select statement which lets me compare these two columns? They are both varchar.
I'm running a db2 database.
I DB2, you can use TO_DATE() to convert both string dates to TIMESTAMP datatypes (note that TO_DATE is a synonym for the TIMESTAMP_FORMAT scalar function).
You can then safely compare them:
to_date(col1, 'dd/mm/yyyy') = to_date(col2, 'yyyymmdd')
I solved it like this.
I used substr:
substr(COLUMN_NAME, 7,4) || substr(COLUMN_NAME,4,2) || sub-str(COLUMN_NAME,1,2)
Posted on behalf of the question asker
Related
I'm using PostgreSQL, but this question is for any modern dbms
I want to basically convert a datetime column which has yyyy/mm/dd into just yyyy/mm
I tried getting months and year separately and using Concat, but the problem is the month comes as a single digit integers for values < 10 and that messes up ordering
select *,
concat(date_part('year' , date_old), '/', date_part('month' , date_old)) as date_new
from table
date _old
date_new
2010-01-20
2010-1
2010-01-22
2010-1
2010-11-22
2010-11
You can use to_char()
to_char(date_old, 'yyyy/mm')
If you want to display your date in the format YYYY-MM then
In PostgreSQL (db<>fiddle) and Oracle (db<>fiddle), use TO_CHAR:
SELECT TO_CHAR(date_old, 'YYYY/MM') FROM table_name;
In MySQL (db<>fiddle), use DATE_FORMAT:
SELECT DATE_FORMAT(date_old, '%Y/%m') FROM table_name;
In SQL Server (db<>fiddle), use CONVERT or, if you are using SQL Server 12 or later, FORMAT:
SELECT CONVERT(varchar(7), date_old, 111) FROM table_name;
SELECT FORMAT(date_old,'yyyy/MM') FROM table_name;
Don't do this.
If you're able to use the date_part() function, what you have is not actually formatted as the yyyy/mm/dd value you say it is. Instead, it's a binary value that's not human-readable, and what you see is a convenience shown you by your tooling.
You should leave this binary value in place!
If you convert to yyyy/mm, you will lose the ability to directly call functions like date_part(), and you will lose the ability to index the column properly.
What you'll have left is a varchar column that only pretends to be a date value. Schemas that do this are considered BROKEN.
I have a column which has dates as texts. Like: '2021_01' (I will reefer this column as TextDate)
I convert it to '2021-01' with this code:
SELECT REPLACE(at.TextDate,'_','-') as DataFormat FROM tableName at
But when I try to cast it to date, or convert it to date, I always get 'Missing expression' errors. I tried this:
SELECT REPLACE(CONVERT(VARCHAR(7), at.TextDate, 126, '_', '-') as date FROM tableName at
But it will give me errors. Any suggestion?
convert means something completely different in Oracle than it does elsewhere. You need the to_date() function:
SELECT TO_DATE(at.textDate, 'YYYY_MM') as DataFormat FROM tableName at
If you want to display it in a particular format then you can either let your client/application do that - most clients by default will use your session's NLS_DATE_FORMAT setting - or explicitly convert it back to a string with the complementary to_char() function.
db<>fiddle
The valid date elements are also in the documentation. You should only convert to a string for display though; while you are manipulating or storing it you should treat it as a date.
How can I filter last 3 months with it?
You need to use Oracle syntax, not SQL Server or other syntax. You also can't refer to a column alias in the same level of query. SO you can recalculate the date value; or as your string format is relatively sane you can convert the target date to a string and compare that, which might allow an index to be used. Something like:
SELECT TO_DATE(at.textDate, 'YYYY_MM') as DataFormat
FROM tableName at
WHERE at.textDate >= TO_CHAR(ADD_MONTHS(TRUNC(SYSDATE, 'MM'), -3), 'YYYY_MM')
db<>fiddle
TO_DATE with appropriate format mask.
Just to know what's what:
SQL> alter session set nls_date_format = 'dd.mm.yyyy hh24:mi:ss';
Session altered.
Code:
SQL> select to_date('2021-01', 'yyyy_mm') from dual;
TO_DATE('2021-01','
-------------------
01.01.2021 00:00:00
SQL>
I want to find the month name in the result from the date given as Jan/10/2015 in SQL.
You can try the DATENAME function in SQL
SELECT DATENAME(month, '2017/09/25');
which in this case will return September.
Date/time functions are notoriously databases dependent -- and you haven't specified the database. That said, your value looks like a string and not a date/time value.
Although you should always store date/time values using appropriate types (which is NOT a string), it looks like you can use string manipulation to do what you want. Most databases support left(), so:
select left(datecol, 3)
In those that don't, use substr() or substring().
You can try this using Oracle:
SELECT TO_CHAR(TO_DATE('Jan/10/2015', 'MM/DD/YYYY'), 'MONTH') as MonthName FROM DUAL;
Oracle SQL automatically converts my field D.START_DT to the following format:
TO_CHAR(D.START_DT,'YYYY-MM-DD')
Which makes it difficult for me to modify my own date format.
I've tried wrapping another TO_CHAR around it with no luck.
TO_CHAR(TO_CHAR(D.START_DT,'YYYY-MM-DD'), 'MM/DD')
And I've tried SUBSTR to select certain characters, with no luck. I think the hyphen is getting int he way.
SUBSTR(TO_CHAR(D.START_DT,'YYYY-MM-DD'), 6, 7) || '/' || SUBSTR(TO_CHAR(D.START_DT,'YYYY-MM-DD'), 9, 10)
What is the work around for this?
I agree with RMAN Express and see no problems converting dates to any format you need...
In case you still have problems try this (first to_char() in outer query is optional):
SELECT to_char(to_date(some_date, 'YYYY-MM-DD'), 'MM/DD') final_date
FROM
(
SELECT TO_CHAR(SYSDATE,'YYYY-MM-DD') some_date -- this is your "auto converted" date
FROM dual
)
/
A DATE datatype has no format. When you see a date printed on a screen, there was something that APPLIED the format you see. Could be a "default" in the program you are using (like SQL Developer) or your NLS setting, etc. But, a DATE datatype has no format. So, you have complete control over the format you see on screen.
The simplest is to use the TO_CHAR function:
select TO_CHAR(D.START_DT,'YYYY') from dual;
returns just the four digit year.
See TO_CHAR date format options.
http://docs.oracle.com/cd/E11882_01/server.112/e26088/sql_elements004.htm#CDEHIFJA
You should always supply the format in your code and not rely on some other "default" to supply it.
I want to format existing dates in a column called mydate in a table called empl. However, I am going no where with this. I have tried
SELECT CONVERT(VARCHAR(10), mydate,103) from empl
but get a missing expression error.
I want to change the current format in the column which is in the format
dd-mm-yy to mm/dd/yy
EDIT: im using oracle
Any suggestions?
If the datatype of the column is DATE, you can use the TO_CHAR() function:
SELECT to_char(mydate, 'mm/dd/yy')
FROM empl ;
Are you able to change the column type to date? Then you could use date_format
The Convert statement you show is for MS-SQL, and you would want code 3 not 103, the 100 series give 4 digit years.
Try:
select to_char(mydate,'MM/DD/YY') from empl
Assuming mydate is stored in date datatype, and using oracle, easy way to do that is:
select to_char(mydate, 'dd/mm/yy') from empl
In Oracle, convert is used to change character set with parameters
(char, destination_char_set, source_char_set)
select TO_CHAR(sysdate, 'MM/DD/YYYY') CHRDATE from dual;